Blockchain systems are commonly viewed as being extremely secure and dependable, but the reality is much more nuanced. Regarding security, while consensus may probably be attack-resistant, it does not address the fact that deployed smart contract code may hold software defects, including vulnerabilities [1]}, [2]}, allowing for certain executions to harm the system. Regarding the general concept of dependability, key properties of the system like ledger integrity, service reliability and service availability are a function of a complex interplay between different mechanisms that target different non-functional properties, which are difficult to check using traditional verification techniques.
